The present invention relates to a method and apparatus for transducing electronic signals from a plurality of analog thermocouple sensors into digital output. The apparatus and method provide for accurate temperature measurement simultaneously from an array of thermocouple sensors and thermal sensor data collection, processing, transmission, and storage. The thermocouple sensors may be attached to an object or substrate to obtain real time temperature measurements with data acquisition rates of 50 per second or more, 100 per second or more, 200 per second or higher.
Thermocouples are commonly used for industrial temperature measurement applications. A typical thermocouple consists of a pair of wires that are made of dissimilar metals and are joined at one end. Thermocouples operate based on a principle that, when the ends of two dissimilar metals are joined and the junction is heated, a current flows in the wire loop. If the circuit is broken, an electromotive force (EMF) measured as a voltage, develops in a heated pair of dissimilar metal wires joined at a junction (hot junction). The EMF produced at a thermocouple junction may be measured by a voltmeter, which introduces a reference junction into the circuit containing the hot junction. The net EMF measured in the complete circuit, therefore, depends upon the temperature at the hot junction Tj as well as the temperature of the reference junction Tr. Consequently, the accuracy of the measured temperature at the hot junction Tj can be improved when the temperature of the reference junction is known and used to correct the EMF measured for the complete circuit. This may be accomplished by placing the reference junction into an environment having a known, preferably fixed, temperature. Controlling the temperature of the reference junction, however, is not practical for many applications. The present invention provides a temperature sensor array in which the temperature of one or more reference junctions is measured and the measured temperature is used to improve the accuracy of measured thermocouple temperatures. This eliminated the need for placing the reference junction into an environment having a known and/or fixed temperature.